In your version, the lines are similar to mine, but the tones are darker. This suggests the "+level" is working differently. Windows BAT scripts need the % doubled to %%. Bash doesn't, so change those to single %.

You probably don't need either "-colorspace sRGB", but they should be harmless.

What version IM do you use? I tested my script on v6.9.5-3 and (using "magick") under v7.0.7-28.